What a gamut is
A display makes color by mixing light from its red, green and blue primaries. The set of colors it can produce by mixing them is its color gamut. Picture all the colors a human eye can see as a rounded shape; a display’s gamut is a smaller triangle drawn inside it, with the three primaries at the corners. Colors inside the triangle can be shown, while colors outside cannot be shown without being altered.
Primaries that are more saturated, meaning they sit nearer the edge of the visible-color shape, give a larger triangle. That is why pure, intense reds and greens are the hardest colors for a basic screen and the ones that wide-gamut screens improve most. The light source and filters matter here: technologies using quantum dots or organic light emitters can produce narrower, purer primaries than a basic white backlight with standard filters, although the result depends on the specific design.
Color spaces are agreed target ranges
A gamut describes what a particular display can do. A color space is a defined target: a standard agreement on where the primaries sit, what the white point is and how brightness values are encoded. Content is made for a color space, and a display tries to reproduce it.
The most common is sRGB, which became the default for web content and ordinary computing. It is a relatively modest range. Wider spaces, such as one commonly used for digital cinema and modern phones (often called P3), and a much wider one used in the specifications for ultra high definition video (often written Rec. 2020), cover more of the visible colors. Few consumer displays reach the widest of these in full, and most content is still made for the smaller spaces.
There is also a related idea, the white point, which is part of what defines a color space and which a display must match for colors to look right.
How coverage is listed
A spec sheet will often say something like “95% of a named space.” This is coverage: the fraction of that space’s colors the display can show. A few cautions help:
- Coverage is not the same as size. A display can cover most of a small space and still be unremarkable, or exceed the space in some directions and miss it in others. Some sheets list “volume” or relative “size,” which compares areas rather than overlap. The two numbers answer different questions.
- Percentages refer to different spaces. A figure for one space cannot be compared with a figure for another. 100% of a small space is a smaller achievement than 90% of a wide one.
- Over 100% can occur. A display with a gamut wider than the space may list more than 100% of size while still not covering every color of the space, so the label alone can mislead.
- Method matters. Measurements depend on how the screen is set and measured, and sheets rarely say. Treat them as approximate.
Wider is not automatically better
It sounds as if a bigger gamut is always an upgrade, but there is an important catch. If content made for a modest space is shown on a wide-gamut display with no adjustment, the colors are stretched. Skin tones go orange, grass turns neon and everything looks oversaturated. For a display to show colors as intended, the system must know the content’s color space and convert the values to the display’s actual primaries. That conversion is called color management.
Well-behaved software handles this, and many modern operating systems and applications do. But not all do, and results can differ between programs on the same screen. Many displays therefore offer a restricted mode that clamps the gamut to the smaller space for content that is not color managed. Switching picture modes is the usual way to select it, usually found among the picture modes in the on-screen menus.
Some people simply prefer a punchier look, and that is a fair taste. The point is that a wide gamut gives capability, not accuracy. Accuracy is a separate matter, covered by color accuracy and its measurement, and depends on calibration and on the display’s processing.
Where gamut matters
For everyday office work and browsing, a modest gamut is generally enough, and many web images are designed for it. Wider gamut tends to matter more for:
- Photo and video work where the final image may go to print or to wide-gamut viewing, which is part of the discussion of editing displays.
- Wide-gamut and high dynamic range video, where the content itself uses more of the range, as high dynamic range explains.
- Design and product work where a specific color, such as a brand color or a fabric, must be judged.
- Graphics that are intentionally vivid, such as game art and cinema material made for wide spaces.
For print, remember that a printer has its own gamut, which differs from a display’s: it can reproduce some colors a screen cannot and vice versa. Neither contains the other.
Gamut and bit depth
A wider range spread over the same number of steps makes each step larger. That is one reason wide-gamut work benefits from higher bit depth: with 8 bits per channel, the steps between levels are coarser in a wide space than in a narrow one, and gradients may show banding more readily.
Reading it cautiously
When you meet a gamut number:
- Check which color space it refers to.
- Check whether it describes coverage or volume.
- Ask whether your content is actually made for that space.
- Treat accuracy as a separate question from range.
A display that covers a wide space and is properly color managed can show more of what the content intends. A display that covers a wide space and is not managed can show exaggerated colors. In both cases the figure on the sheet is only the beginning of the answer.